EP0187409B1

EP0187409B1 - Drill motor assembly with gimbal normality and clamp-up capability

Info

Publication number: EP0187409B1
Application number: EP85201977A
Authority: EP
Inventors: Quentin T. Woods
Original assignee: Boeing Co
Current assignee: Boeing Co
Priority date: 1984-12-28
Filing date: 1985-11-26
Publication date: 1989-03-22
Also published as: EP0187409A1; DE3568953D1; US4613262A

Description

The invention relates to a drilling apparatus as defined in the introductory part of claim 1.
A drilling apparatus of this kind is known from US-A-3 973 859. With this known apparatus workpieces having compound curved surfaces can be drilled. The drilling axis can be positioned such that it is normal to the surface of the workpiece at the point where a bore must be drilled. To establish. the position of the drilling axis and thereby the position of the first housing relative to the second housing, the workpiece is first scanned by a camera so that of each point of the workpiece information is obtained with regard to the curvature at each point. The camera is replaced by a drilling tool and this drilling tool is positioned by means of the information obtained before, such that the drilling axis can be posioned normal to the workpiece at the point a bore must be drilled.
This known apparatus is very complex and the operation thereof is time consuming. For each bore to be drilled first the information about the curvature must be obtained by means of the scan camera. Only after the scan camera is replaced by the drilling tool, the bore can be drilled.
The invention has for its object to provide a drilling apparatus of the kind said forth above, which is relatively simple and does not need time consuming preparations for its operation.
According to the invention this is achieved by a drilling apparatus of the mentioned kind, having the features as mentioned in the characterizing part of claim 1. By positioning the pressure feet against the workpiece, the datum plane as defined by the pressure feet will be positioned substantially parallel to and coincident with a plane tentioned to the surface of the workpiece in the point of intersection of the drilling axis with said surface. As the datum plane is perpendicular to the drilling axis, the drilling axis in this way will be positioned normal to the workpiece surface at the point where the bore must be drilled.
In this way the drilling member can be moved with the drilling apparatus directly against the workpiece and the drilling member will be automatically positioned normal to the surface of the workpiece without any complex and time consuming preparations.
A preferred embodiment of the apparatus as characterized in claim 3 has the adavantage that the actual point at which the drilling member will contact the workpiece and therefore the actual position of the bore to be drilled, is substantially not influenced by the pivoting position of the drilling axis, so that the drilling position can be accurately defined and programmed.
Further preferred embodiments are characterized in the subclaims.
An important advantage to the present invention is that it provides a quick and easy means for drilling a bore normal to the surface of a workpiece.
Another advantage of the present invention is that it provides a means for clamping the drilling apparatus to a workpiece with sufficient force so that the apparatus will not translate relative to the workpiece surface as the bore is drilled. This has a number of effects. First, it eliminates drill skid. Second, it ensures that the bore will be drilled normal to the surface of the workpiece for its entire length. Third, when a countersink is provided in the bore, a sufficient clamp-up force will ensure that the countersink remains in concentric relationship relative to the drilling axis. Further, clamp-up pressure ensures that no gaps occur between multi strata in the workpiece which thereby eliminates burrs and chips between the layers. The amount of pressure applied also takes into account the structural stability of the workpiece itself.
Still another advantage to the present invention is that it provides a datum plane that may be used as a depth register for determining the depth of the bore as it is being drilled. This is important when drilling bores that, for example, have a countersink portion for receiving the head of a rivet or the like. It is critical to know the point at which to stop drilling the bore so that the rivet can fit into the bore with the rivet head being substantially flush with the surface of the workpiece.
Still another advantage to the present invention is that it is well suited for adaptation to computerized control. The rotation and advancement ofthe drilling bit for bore depth may be controlled by a computer. Likewise, control of clamp-up pressure may also be computer controlled.
Referring now to the drawings, like reference numerals refer to like parts throughout the various views, and wherein:

Fig. 1 is an elevational cross-sectional view of a drilling apparatus constructed in accordance with a preferred embodiment of the invention;
Fig. 2 is a pictorial view of a common drill press and shows the drilling apparatus of Fig. 1 mounted thereto for drilling a bore in a workpiece;
Fig. 3 is a pictorial view of a robot arm and shows the apparatus of Fig. 1 mounted to the end of the arm in such a manner so that the arm may be used to position the apparatus adjacent a workpiece;
Fig 4 is a view much like Fig 1 but shows another embodiment of the drilling apparatus wherein the apparatus is shown mounted to carriages of an automatic traversing drilling unit;
Fig. 5 is an enlarged fragmentary view of the lower portion of the drilling apparatus shown in Fig. 4, and shows the drill bit of the apparatus being normalized relative to the surface of a workpiece;
Fig. 6 is a view like Fig. 5 but shows the drilling bit being normalized for a workpiece surface having a different curvature than that shown in Fig. 5;
Fig. 7 is an enlarged fragmentary pictorial view, shown in partial section, of a gimbal member and pressure feet which form the lower portion of the drilling apparatus shown in Figs. 4-6; and
Fig. 8 is a cross-sectional view taken along line 8-8 in Fig. 4.

Referring now to the drawings, and first to Fig. 1, therein is shown at 10 a drilling apparatus constructed in accordance with a preferred embodiment of the present invention. The apparatus 10 is positioned adjacent a workpiece 12 for drilling a bore therein. In general form, the apparatus 10 includes an inner housing 14 that is connected to an outer housing 16 by a gimbal member 18. The inner housing 14 supports a drill bit 20 which is driven by a spindle shaft 22. The spindle shaft 22 is received within the inner housing and extends downwardly through an opening 23 in the gimbal member 18. The spindle shaft has a rotating portion 24 and a nonrotating portion 26 which are connected together by a rotary thrust coupling 28.
The upper portion of the inner housing 14 has a feed motor 30 connected to threads 31 on the nonrotating portion 26 of the spindle shaft 22. The feed motor 30 moves the spindle shaft 20 axially toward and away from the workpiece 12. In this manner, the drill bit 20 may be advanced toward and against the surface 32 of the workpiece 12 with a desired feed rate. The lower portion of the inner housing 14 includes a spindle motor 34 that is connected to a splined rotating portion 24 of the spindle shaft 22. Rotation of the rotating portion 24 causes the drill bit to rotate for the purpose of drilling a bore.
In Fig. 1, the gimbal member 18 is fixedly connected to the inner housing 14 by means of an annular, outwardly radiating flange portion 36, which is bolted to the casing of the spindle motor 34. The gimbal member 18 includes a portion 38 having a spherical surface. The outer housing 16 includes an annular bearing surface 40 shaped to slide adjacent the spherical surface portion 38 of the gimbal member 18. The sliding movement of the bearing surface 40 relative to the spherical surface 38 permits the inner housing 14 to pivot relative to the outer housing 16. This, of course, also permits the spindle shaft 22 and drill bit 20 to pivot.
In preferred form, the gimbal member 18 includes three pressure feet 42 which extend downwardly from the gimbal member. The pressure feet 42 are spaced equidistant from each other and abut against the surface 32 of the workpiece 12. The longitudinal axis of the drill bit 20 (and the spindle shaft 22) is positioned centrally between the pressure feet 42. This is best shown in Figs. 7 and 8, which illustrate a second embodiment of the invention that is to be described later.
A datum plane 44 is defined by the locations 46 where the pressure feet 42 contact the workpiece surface 32. The datum plane 44 intersects each location 46 where a pressure foot contacts the workpiece surface 32. The spherical surface portion 38 of the gimbal member 18 is defined by a radius 50 which originates at the point where the axis 45 of the bit 20 intersects the datum plane 44. This point of intersection defines a drilling point 48 for drilling a bore in the workpiece 12. Therefore, as can be seen from the drawings, the pressure feet 42 define a datum plane 44 which is substantially tangent to the surface 32 of the workpiece 12. The drilling point 48 for the bore is positioned on the datum plane 44 and therefore will also be substantially tangent to the surface 32. What this means is that as the apparatus 10 is positioned adjacent a workpiece, the pressure feet 42 will abut against the surface of the workpiece causing the inner housing 14 to pivot relative to the outer housing 16. Since the center of the gimbal member spherical portion 38 is located at the drilling point 48, such pivoting movement will also pivot the drill axis 45 into a position that is substantially normal to the workpiece surface. A person skilled in the art would realize that the combination of the spacing between the pressure feet 42 and the curvature of the workpiece surface 32 would affect the location of the datum plane 44 with regard to its tangency relative to the workpiece surface. However, proper spacing of the pressure feet 42 will result in a datum plane 44 that is positioned substantially tangent to the surface, resulting in a bore that is drilled substantially normal to the workpiece surface.
The apparatus 10 shown and described herein is to be used in conjunction with some sort of means for positioning the apparatus adjacent a workpiece. For example, and referring now to Fig. 2, the apparatus 10 is well suited for adaptation to a standard drill press 52. The apparatus 10 is shown in this Fig. mounted to a spindle arm 53 which is vertically movable. Alternatively, and referring now to Fig. 3, the apparatus 10 could be used in conjunction with an automatically controlled robot 54. The robot 54 would have an arm portion 55 that grasps the apparatus 10 by means of gripping members 56, 58 for positioning the apparatus adjacent a workpiece. Referring back to Fig. 1, the apparatus 10 is shown wherein the outer housing 16 is held by the gripping members 56, 58 of the robot 54.
When the apparatus is positioned adjacent a workpiece, the pressure feet 42 first abut against the surface of the workpiece, thereby causing the drill axis 45 to assume a normal position relative to the workpiece surface 32. A pneumatic actuator, indicated generally by arrow 60, and constructed as a portion of the outer housing 16, may provide a clamp-up force for clamping the pressure feet 42 against the workpiece surface 32. A first portion 62 of the outer housing is connected to the gripping members 56, 58 of the positioning means. A second portion 64 of the outer housing is directly connected to the annular bearing surface 40, which slides adjacent the spherical surface portion 38 of the gimbal member 18. In preferred form, both the first and second portions are cylindrical members, wherein the outer sidewall 66 of the second portion is in sliding contact with the inner sidewall 68 of the first portion 62. The lower part of the first portion 62 projects radially outwardly
so as to provide an annular chamber 72 between the outer sidewall 66 of the second portion 64, and the inner sidewall 68 of the first portion. The annular chamber 72 is divided by an outwardly projecting flange 78 that is connected to the outer sidewall 66 of the second portion 64 of the outer housing 16. This flange 78 separates the chamber 72 into upper and lower chambers 74, 76. Air inlet/ outlet ports 80, 82 may be connected to each of the chambers 74, 76. By pressurizing the upper chamber 74 with air, the second portion 64 of the. outer housing is thrust downwardly with respect to the first portion 62. This thrust is transferred by the bearing surface 40 onto the spherical surface portion 38 of the gimbal member, and is further transmitted to the pressure feet. The thrust provided by the actuator 60 therefore provides a clamp-up force that ensures that the apparatus 10 will remain in a stationary position relative to the workpiece surface 32 as the bore is drilled. For example, by having a sufficient clamp-up force, there will be little or no sideways translation of the drill bit 20 as the bore is drilled. In addition, if the workpiece comprises several layers of the material, the clamp-up force may be used to hold the several layers together as the bore is drilled. A seal 70 may be provided between the outer sidewall 66 of the second portion 64 and the inner sidewall 68 of the first portion 62 for preventing air leakage from the upper and lower chambers 74,76.
In the embodiment shown in Fig. 1, when the apparatus 10 is moved away from the workpiece 12, the spherical surface portion 38 of the gimbal member 18 is held adjacent the bearing surface 40 of the outer housing 16 by means of a diaphragm spring 84. When the pressure feet 42 are not adjacent a workpiece the inner housing 14 is free to swing back and forth between the positions shown by the dashed lines 86 and 88. The top portion 90 of the outer housing 16 may be provided with an opening 92 through which the nonrotating portion 26 of the spindle shaft 22 extends. The opening 92 would provide a structural constraint limiting the amount of back and forth movement of the spindle shaft 22. The opening 92 may be covered with a rubber material 94 to prevent the spindle shaft 22 and/or the outer housing 16 from being damaged when the apparatus 10 is moved from position to position adjacent a workpiece, or when the apparatus is moved between different workpieces.
Another embodiment of the invention is shown in Figs. 4-8. In this other embodiment, the apparatus 10 is shown mounted to an automatic traversing drilling unit, indicated generally by 96, wherein the apparatus 10 may be used to drill a series of holes in a body panel or the like.
The apparatus 10 is shown connected to a pair of carriages 98, 100 of the unit 96, wherein one carriage is positioned on each. side of the apparatus. The apparatus 10 is attached to the carriages 98, 100 by means of outwardly extending linkage members or rods 102, 104.
In basic form, the apparatus 10 shown in Figs. 4-8 is the same as the apparatus shown in Fig. 1, with a few alterations. Referring now to Fig. 4, the apparatus 10 shown therein has the same gimbal member 18, with the gimbal member having a spherically shaped surface portion 38. The outer housing 16 is fixedly connected to the linkage rods 104 and 102 and therefore cannot move relative to the carriages 98, 100 of the traversing drilling unit 96. A clamp-up motor 112, which in this case may be in the form of a hollow nut electric motor, is connected to the first and second portions 110, 108 of the outer housing 16 in such a manner so that the clamp-up motor may be operated to slide the second portion 108 relative to the first 110. Therefore, moving the second portion 108 downwardly relative to the first portion 110 would cause the bearing surface 40 to thrust against the spherical surface portion 38 of the gimbal member. This in turn would cause the pressure feet 42 to clamp-up against the surface 32 of the workpiece 12.
The embodiment shown in Figs. 4-7 includes an annular support shoulder 112 which prevents the inner housing 14 from falling free of the outer housing 16 when the apparatus 10 is lifted away from the workpiece surface 32.
The drill bit 20 is driven in much the same manner as the embodiment shown in Fig. 1. In the later embodiment, however, the rotating portion of the spindle 22 is driven by an air driven motor 106. The spindle 22 is hollow for providing an air passageway 114 to supply air to the motor 106. Air for driving the motor 106 may be input through an end of the spindle shaft 22, which is indicated generally by arrow 116. The spindle shaft 22 is advanced toward the workpiece by an electric feed motor 118 mounted to the top portion of the apparatus 10. A linkage arm 120, connected to both the feed motor 118 and the clamp-up motor 112, prevents rotation of the feed motor 118 relative to the outer housing 16.
Although two embodiments of the invention have been presented and described above, a person skilled in the art would realize that other embodiments of the invention could be made without departing from the scope thereof. It is not intended that the invention shall be limited in any way by the above description. The scope of the invention shall be limited only by the appended claims which follow, in accordance with the established doctrines of patent claim interpretation.

Claims

1. A drilling apparatus (10) comprising a drilling member (20) rotatable about a drilling axis (45) for drilling a bore in a workpiece (12), and comprising drive means (34, 30) for rotating said drilling member (20) and for advancing said member (20) toward and against the workpiece (12) to drill said bore, said drilling member (20) and drive means (34, 30) being mounted to a first housing (14), said first housing being mounted to a second supporting housing (16) by gimbal means (18) permitting gimbal movement of said first housing (14) relative to said second housing (16) about a point on said drilling axis (45) and means for establishing a drilling position of said first housing (14) relative to said second housing (16) with regard to the workpiece (12) characterized in that said means for establishing a drilling position comprising pressure feet (42) mounted to said first housing (14) adjacent said drilling member (20), for contacting said workpiece (12), said pressure feet (42) defining a datum plane (44) perpendicular to said drilling axis (45).

2. The apparatus according to claim 1, characterized in that said first housing is an inner housing (14) receiving said drive means (30, 34) and supporting said drilling member (20), and said second housing is an outer housing (16) surrounding said inner housing (14).

3. The apparatus according to claim 1 or 2, characterized in that said gimbal means (18) permitting gimbal movement of said first housing

(14) relative to said second housing (16) about the point of intersection (48) of said drilling axis (45) with said datum plane (44).

4. The apparatus according to claim 2 or 3, characterized in that said gimbal means including a surface (38) connected to said inner housing (14) having a spherical-portion defined by a radius (50) that originates at said point of intersection (48) with said outer housing (16) including a bearing surface (40) shaped to slide adjacent said spherical surface portion (38).

5. The apparatus of claim 3, characterized by a plurality of pressure feet (42) which abut against said workpiece (12), said pressure feet (42) being arranged equidistant from said point of intersection (48).

6. The apparatus according to one of the preceding claims, characterized by positioning means (53), connected to said second housing (16), for moving said drilling apparatus (10) and for holding it adjacent said workpiece (12), wherein clamp-up means (60) thrusts said feet

(42) against said workpiece (12) with a certain preselected clamp-up force.

7. The apparatus according to claim 5, characterized by thrust sensor means for sensing said preselected clamp-up force with which said pressure feet (42) contacting said workpiece (12).

8. The apparatus according to claim 6 or 7, characterized in that said clamp-up means (60) is operatively connected to said second housing (16) in a position between said positioning means (53) and said gimbal means (18).

9. The apparatus according to claim 7 or 8, characterized in that said thrust sensor means comprising strain gauge means mounted to said outer housing (16) in a position so as to be responsive to the amount of clamp-up force said feet (42) place on said workpiece (12).

10. The apparatus according to one of the preceding claims, characterized in that said drive means includes a spindle shaft (22) connected to said drilling member (20), said shaft having a rotating portion (24) that rotates about said drilling axis (45), and a nonrotating portion (26), wherein said nonrotating portion (26) is connected to a feed motor (30) for advancing said shaft (22) towards said workpiece (12), and wherein said rotating portion (24) is connected to a spindle motor (34), said spindle motor (34) rotating said shaft (22) to cause said drilling member (20) to rotate, and a rotary thrust coupling member (28) connecting said rotating portion (24) to said nonrotating portion (26).

11. The apparatus according to one of the preceding claims 6-10, characterized in that said clamp-up means comprising first (62) and second (64) portions of said outer housing (16) said first (62) and second (64) portions being movable relative to each other, wherein said first portion (62) is connected to said positioning means (53), and wherein said second portion (64) is connected to said bearing surface (40) of said outer housing (16) and actuator means (60) for moving said second portion (64) relative to said first portion (62), to cause said bearing surface (40) to thrust against said spherical surface portion (38) of said gimbal member (18).

12. The apparatus according to claim 11, characterized in that said actuator means comprising an electric clamp-up motor operatively connected to said first (62) and second (64) portions in a manner so as to move said second portion (64) relative to said first portion (62).

13. The apparatus according to claim 11, characterized in that, said actuator means comprises a hydraulic actuator operatively connected to said first (62) and second (64) portions in a manner so as to move said second portion (64) relative to said first portion.

14. The apparatus according to claim 11, characterized in that said actuator means comprising a pneumatic actuator (60) operatively connected to said first (62) and second (64) portions in a manner so as to move said second portion (64) relative to said first (62) portion.